What would you do?

Car is 1996 Corvette with LT1 engine. Codes are P0131, P0134, and P1133. I plan on changing the O2 sensor but which one? I think I know which one, but just to be sure that's all I'm saying.
Let's see if I'm right or wrong. Which one would you change? Do I really need the special tool? Thanks in advance.
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My guess won't count on which one to change first but, I'd try the PO1133 code (HO2S Insufficient Switching Bank 1 Sensor 1) first as it may affect both sensors. Will you need the special tool answer is yes, and don't buy a cheap one.
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